This project explores basic etiologic and pathogenetic mechanisms in congenital heart disease, through the study of strains of dogs having hereditary lesion-specific defects in cardiovascular development. The malformations to be studied are: Patent ductus arteriosus (PDA), pulmonic stenosis, fibrous ring subaortic stenosis, and conus septum defects (including ventricular septal defects and tetralogy of Fallot). The pathogenesis of each defect will be studied by retrograde embryologic analysis, utilizing serial sectioning and wax plate reconstruction of the heart at critical stages of development. The pathogenesis of left heart failure and pulmonary hypertension in pups with hereditary PDA, and the pathogenesis of coronary arterial and myocardial lesions in subaortic stenosis will be studied by hemodynamic and anatomic methods. BIBLIOGRAPHIC REFERENCE: Pyle, R.L., Patterson, D.F., Chacko, S.: The pathology and genetics of discrete subaortic stenosis in Newfoundland dogs. Am. Heart J. 1976, in press.